(1) Field of the Invention
The present invention relates to a heat-sensitive color-forming recording material. More particularly, the present invention relates to a heat-sensitive recording material which is sensitized without substantial increase of the fog density.
(2) Description of the Prior Art
The combination of a leuco pigment and a color developer composed of an acidic substance has been widely used for recording of informations, for example, heat-sensitive recording, pressure-sensitive recording and electrostatic photographic recording. For example, as a recording element for heat-sensitive recording, there has been used a recording material comprising a recording layer formed on a substrate, said recording layer being obtained by dispersing a leuco pigment which is colorless or has a light color in the normal state and a phenol which is solid at normal temperature but is heat-fusible, in a polymeric binder independently in separate phases.
In this heat-sensitive recording material, color formation is effected when the leuco pigment and phenolic color developer are reacted with each other in the state activated by heat, especially in the fused state. Since fusion of the phenolic color developer or leuco pigment is not caused unless the temperature is considerably high, the heat sensitivity of the recording material is low and the density of a recorded image is generally low. Furthermore, since recording must be carried out at a high temperature, this recording material is disadvantageous in that a high temperature heat source is necessary. Moreover, the temperature of a transportation system in a heat-sensitive recording apparatus is elevated, and therefore, fogging is readily caused to occur.